The present invention relates to a finisher for use with a copier, laser printer or similar image forming apparatus and, more particularly, to a finisher having a function of sorting or stacking sheets which are sequentialy driven out of the apparatus and a function of binding stacks of such sheets one by another.
A finisher such as a sorter is extensively used with a copier or similar image forming apparatus for stacking recorded sheets on trays or bins in a sort mode or a stack mode. For example, a finisher disclosed in Japanese Patent Publication No. 44662/1988, for example, has a plurality of trays which are sequentially movable tgo a sheet discharge position for receiving recorded sheets from an image forming apparatus. An advanced finisher has even a function of stapling stacks of sheet distributed to the individual bins one by one. This kind of finisher, i.e., sorter/stapler may have a stapler which is movable to staple positions each being associated with respective one trays so as to sequentialy staple sheet stacks loaded on the trays, as taught in Japanese Patent Publication No. 302/1989 by way of example. Generally, the sorter/stapler is an attempt to add a stapling function to a sorter as an extra function. Therefore, some problems have been left unsolved in building a stapler in the copnventional sorter, as follows.
Sheets stacked on each tray by a sorter are often curled or otherwise deformed. Then, it is likely that not all of such deformed sheets are pulled out from the tray to the staple position, i.e., some sheets remain on the tray without being stapled. Moreover, the sheets are apt to bend along the curl while being moved toward the staple position. Generally, a sorter without a stapling function stacks sheets on each tray such that they gather at the center of the tray. Hence, a sorter needs an independent jogger for repositioning the sheets stacked at the center of the tray at a reference position which is close to a staple position located at one side of the tray. Furthermore, a conventional mechanism for moving a stack of sheets from the tray to the staple position is extremely complicated in construction.